Demonstration and Scale Up of Photovoltaic (PV) Solar Water Pumping Technology

and System for the Conservation of Grassland and Farmland in China

SolarGrass

Photovoltaic Solar Water Pumping Technology and System in China

Desertification of grasslands is regarded as one of the major environmental and economic problems of China, affecting around 400 million people and causing a loss of up to 8 billion U.S. dollars per year. The pasture areas are mainly distributed in the dry areas in the northern and northwestern regions in China. Approximately 30% of the Chinese grasslands, covering an area of nearly 4 million km2, are degraded and it is thought that overgrazing, combined to the unfavorable climatic conditions, is the most important factor causing desertification combined. Conserving the pasture areas becomes urgent to restore the ecological system in China.

One simple method is to limit the animal production per unit of area. However, this might introduce negative impacts of lowering the already low farmers’ incomes due to the reduced number of livestock. An innovative solution to increase the productivity of the grassland thus maintaining and even improving the farmers’ living standards while implementing ecological conservation is required.

In the pasture land in Qinghai and Tibet in China, it has been observed that there are available water resources which can be used for irrigation of grassland. Grass production can increase over 10 to 30 times by introducing irrigation. However, the major technical obstacle for water pumping in remote areas is represented by the lack of electricity access. The abundance of solar energy resources makes photovoltaic (PV) technology a feasible and reliable solution for water pumping, supplying water for irrigation and drinking water.

In order to scale up solar water pumping into wider range, an integrated research and development should be carried out by reducing the cost and increasing the system stability and efficiency.

Photovoltaic (PV) water pumping systems

Water pumping system is one of the most successful applications of stand-alone photovoltaic (PV) systems in developing countries as well as in remote areas where there is no electrification. As described in the figure below, a PV water pumping system is mainly composed by PV array, power conditioning system (DC/DC controller or DC/AC inverter), DC or AC motor pumping system and a storage-distribution system. The photovoltaic array converts directly solar energy into electricity to feed the motor-pump system. The power conditioning system is an interface between the solar modules and the motor pump improving the performances. The pump raises the water up to a storage tank or directly to the distribution system. The main usages of this technology are providing drinking water for villages, water for livestock and water for irrigation purposes.

The exploitation of a free energy source like solar energy makes PV pumping systems a sustainable alternative to the traditional pumping system driven by diesel generator. Even under an economic point of view, PV water pumping systems proved to have numerous advantages on the fossil fuel driven system especially in terms of life cycle cost (LCC) and unit water cost (UWC). The major strengths of PV water pumping systems are:

• no fuel demand

• low maintenance

• automatic startup

• no batteries

• no pollution

• no disturbance

The rise of fossil fuels price and, simultaneously, the decrease of PV modules price make this technology more attractive outlining a potential niche market for this application. Indeed the economic benefits resulting from the PV pumping system installation are not only restricted to the end users since the overall project involves many stakeholders including companies, experts and consultants from different fields.